The U.S. Supreme Court will hear an appeal on Tuesday from the parents of a Mexican teenager killed along the U.S.-Mexico border by an American agent, in a case that could determine if foreigners injured abroad have the right to sue in U.S. courts.

U.S. officials did not prosecute Border Patrol Agent Jesus Mesa Jr. followingthe June 2010 shooting death of 15-year-old Sergio Adrian Hernández Guereca, who was standing in Mexico when Mesa fired from Texas.

When the teen’s parents tried to sue, a lower federal court and an appeals court both ruled that they couldn’t pursue the case because the teen wasn’t in the U.S., and therefore wasn’t covered by American Constitutional rights that protect against unwarranted searches and seizures.

Lawyers for Hernández Guereca’s parentssaid it’s their last chance for justice, since the court’s ruling will ultimately determine if they have the right to sue.

Killed on a dare to touch a fence?

Hernández Guereca’s family said that he was playing chicken with some friends along the border on June 7, 2010. The pals dared one another to touch an 18-foot fence on the American side of the border and then run back to Mexican soil.

Mesa was patrolling the border when he spotted the teens. He detained one person who was on the U.S. side as the others fled back to Mexico. The border agent then fired at Hernández Guereca, killing him.

Declining to press charges against Mesa, the U.S. Justice Department claimed he was trying to stop “smugglers attempting an illegal border crossing.” Officials said Mesa opened fire on Hernández Guereca after the teen started throwing rocks at him, a claim the teen’s family denies.Cellphone video, shot by a witness on the Mexican side of the border who saw Mesa confront the teens, appears to show Hernández Guereca running away from Mesa — not throwing rocks — when he was shot and killed.

In the absence of criminal changes, the family filed a civil suit against Mesa, which was dismissed by a Texas judge. They appealed, and in June 2014 a three-judge panel from the 5th U.S. Circuit Court of Appealsoverturned the lower judge’s decision, saying the family could sue.

The panel’s decision in favor of the family was knocked down by the full nine-judge Court of Appeals in April 2015, prompting them to appeal to the Supreme Court.

Fourth Amendment may not stop at the border

The decision of whether Hernández Guereca’s family has the right to sue hinges on the question of whether or not the teen had Fourth Amendment protection.

The vaguely-worded constitutional amendment protects against unwarranted searches and seizures from the government and, since the 1980s, courts have interpreted it to include the use of deadly force — an “unwarranted seizure of your body,” said Andrew Kent, a professor of law at Fordham University School of Law.

The Supreme Court will ultimately be deciding if a non-U.S. citizen has constitutional protection outside of the U.S., Kent said.

“If the court decides that the Fourth Amendment no longer stops at the border, there are a lot of implications,” Kent said.

While the Hernández v. Mesa case will immediately impact Guereca’s family’s ability to sue Mesa, it could also provide a ruling for other Mexican nationals injured or killed on Mexican soil by U.S. border agents. There have beenat least six of those cases since 2010.

But the ruling could open the door for other issues too, Kent said, and may pave the way for non-citizens to sue the U.S. for a variety of possible Fourth Amendment infractions.

If those rights apply outside of the U.S., non-Americans may be able to challenge the government’s electronic surveillance programs. Drone attacks in the Middle East could also be challenged, Kent said, noting that, while striking non-U.S. citizens overseas has been subject to international human rights, such attacks have never faced constitutional challenges.

“That would certainly encourage folks to bring lawsuits,” he said.

A ruling in favor of the family would be the second time the Supreme Court has decided that, sometimes, non-citizens have U.S. constitutional rights when they’re outside of the nation’s borders, Kent said.A 2008 decision said that detainees at Guantanamo Bay have a constitutional right to challenge their detentions.